Queensland officials are still working out the full impact of coral bleaching on the Great Barrier Reef, but the evidence suggests that 2016 was worse than expected.

"The amount of coral that died from bleaching in 2016 is up from our original estimates," said Great Barrier Reef Marine Park Authority chairman Russell Reichelt, "It's expected we'll also see an overall further coral cover decline by the end of 2017."

Aerial and in-water surveys by the Marine Park Authority, Queensland Parks and Wildlife Service, Australian Institute of Marine Science and the ARC Centre of Excellence for Coral Reef Studies showed increasing impact from north to south.  It was feared that 22-percent of shallow water corals died in 2016, but the surveys showed it was actually more than that - 29 percent.

The most severe bleaching north of Port Douglas, where 70 percent of shallow water corals had died along with significant variability between and within reefs.